I was wondering if American people knew about the project prior to the detonation of the bombs in Japan. If they knew about it, did they properly understand what was being done? Did they support it? Thanks.
The general public didn't know anything about it. Interested observers might surmise what was going on though, as u/restricteddata discusses here. I'm sure more can be said though!
https://www.reddit.com/r/AskHistorians/comments/7mqaku/was_anybody_able_to_guess_what_the_manhattan/
It was a huge project, as they point out it used about 1% of the whole US civilian labor force, but while lots of people were involved in some way the degree of compartmentalization was extraordinarily high for the period. Some discussion on that from the same user is here: